How to make an object transparent
To do this in Cycles, choose cycles render and open node editor.

Create your base material for the football (this should be what it should look like if there wasn't any transparency on it.



Then mix this with a transparent shader, and make any necessary shader tweaks to give it the appearance you're looking for.



The cylinder is positioned inside the sphere, the cube behind it

Please keep in mind that if you prefer to use the Blender Internal Engine, that's perfectly fine, this is just a way to do it using Cycles.